The present invention is directed to ink jet printing processes. More specifically, the present invention is directed to ink jet printing processes using recording sheets containing microspheres on at least one surface thereof. One embodiment of the present invention is directed to a printing process which comprises (a) incorporating into an ink jet printing apparatus containing an aqueous ink a recording sheet which comprises (1) a substrate; (2) a first coating layer which comprises a binder and microspheres; (3) a second, ink-receiving coating layer situated so that the first coating layer is between the second, ink-receiving coating layer and the substrate, said second, ink-receiving layer comprising a hydrophilic binder and microspheres; (4) an optional antistatic agent; (5) an optional biocide; and (6) an optional filler; and (b) causing droplets of the ink to be ejected in an imagewise pattern onto a surface of the recording sheet containing microspheres, thereby generating images on the recording sheet. Another embodiment of the present invention is directed to a printing process which comprises (a) incorporating into an ink jet printing apparatus containing an aqueous ink a recording sheet which comprises (1) a substrate; (2) a first coating layer which comprises a binder and microspheres; (3) a second, ink-receiving coating layer situated so that the first coating layer is between the second, ink-receiving coating layer and the substrate, said second, ink-receiving layer comprising a hydrophilic binder and microspheres; (4) an optional antistatic agent; (5) an optional biocide; and (6) an optional filler; (b) causing droplets of the ink to be ejected in an imagewise pattern onto a surface of the recording sheet containing microspheres, thereby generating images on the recording sheet; and (c) thereafter exposing the substrate to microwave radiation, thereby drying the recording liquid on the recording sheet.
U.S. Pat. No. 5,137,939 (Siddiqui), the disclosure of which is totally incorporated herein by reference, discloses films or sheets of linear polyester containing glass spheres having a certain particle size distribution and in a certain amount based upon the weight of the polyester film. The addition of the glass spheres improves several properties of the film, including the dynamic coefficient of friction. Preferably, a second film additive, fumed silica, of a controlled particle size distribution and weight, is additionally added to the film. The addition of the fumed silica additionally improves several properties of the polyester film, including the static coefficient of friction of the film.
U.S. Pat. No. 4,166,152 (Baker et al.), the disclosure of which is totally incorporated herein by reference, discloses infusible, solvent-insoluble, solvent-dispersible, inherently tacky, elastomeric polymeric microspheres which are formed from non-ionic monomers and comprise at least one oleophilic water-emulsifiable alkyl acrylate or methacrylate ester. The microspheres are prepared by a suspension polymerization technique which includes the use of an ionic suspension stabilizer.
U.S. Pat. No. 3,561,337 (Mulkey) discloses a sheet material having a transparent backing coated with a layer containing a polymeric binder and particles of solid material which is insoluble in the binder. The refractive index of the solid material varies from that of the binder by at most .+-.0.6. The surface of the layer is ink receptive and, by printing on that surface, a transparency is obtained.
U.S. Pat. No. 5,212,008 (Malhotra et al.), the disclosure of which is totally incorporated herein by reference, discloses a recording sheet which comprises a substrate; a first coating in contact with the substrate which comprises a crosslinking agent selected from the group consisting of hexamethoxymethyl melamine, methylated melamine-formaldehyde, methylated urea-formaldehyde, cationic urea-formaldehyde, cationic polyamine-epichlorohydrin, glyoxal-urea resin, poly (aziridine), poly (acrylamide), poly (N,N-dimethyl acrylamide), acrylamide-acrylic acid copolymer, poly (2-acrylamido-2-methyl propane sulfonic acid), poly (N,N-dimethyl-3,5-dimethylene piperidinium chloride), poly (methyleneguanidine) hydrochloride, poly (ethylene imine) poly (ethylene imine) epichlorohydrin, poly (ethylene imine) ethoxylated, glutaraldehyde, and mixtures thereof; a catalyst; and a polymeric material capable of being crosslinked by the crosslinking agent and selected from the group consisting of polysaccharides having at least one hydroxy group, polysaccharides having at least one carboxy group, polysaccharides having at least one sulfate group, polysaccharides having at least one amine or amino group, polysaccharide gums, poly (alkylene oxides), vinyl polymers, and mixtures thereof; and a second coating in contact with the first coating which comprises a binder and a material selected from the group consisting of fatty imidazolines, ethosulfate quaternary compounds, dialkyl dimethyl methosulfate quaternary compounds, alkoxylated di-fatty quaternary compounds, amine oxides, amine ethoxylates, Imidazoline quaternary compounds, alkyl benzyl dimethyl quaternary compounds, poly (epiamines), and mixtures thereof.
U.S. Pat. No. 4,865,914 (Malhotra), the disclosure of which is totally incorporated herein by reference, discloses a transparency comprising a supporting substrate and thereover a blend comprising poly(ethylene oxide) and carboxy methyl cellulose together with a component selected from the group consisting of (1) hydroxypropyl cellulose; (2) vinylmethyl ether/maleic acid copolymer; (3) carboxymethyl hydroxyethyl cellulose; (4) hydroxyethyl cellulose; (5) acrylamide/acrylic acid copolymer; (6) cellulose sulfate; (7) poly(2-acrylamido-2-methyl propane sulfonic acid); (8) poly(vinyl alcohol); (9) poly(vinyl pyrrolidone); and (10) hydroxypropyl methyl cellulose. In addition, papers with the aforementioned coatings are disclosed.
U.S. Pat. No. 4,592,954 (Malhotra), the disclosure of which is totally incorporated herein by reference, discloses a transparency for ink jet printing comprising a supporting substrate and thereover a coating consisting essentially of a blend of carboxymethyl cellulose and polyethylene oxides. Also disclosed are papers for use in ink jet printing comprising a plain paper substrate and a coating thereover consisting essentially of polyethylene oxides.
U.S. Pat. No. 5,254,403 (Malhotra), the disclosure of which is totally incorporated herein by reference, discloses a recording sheet which comprises a substrate and an image receiving layer comprising a mixture of (a) a polymer capable of forming a latex and selected from the group consisting of poly (vinyl chloride), ethylene-vinyl chloride copolymers, poly (vinyl acetate), carboxylated poly (vinyl acetate), ethylene-vinyl acetate copolymers, polymers containing acrylate monomers, poly styrene, styrene-butadiene copolymers, carboxylated styrene-butadiene copolymers, butadiene-acrylonitrile copolymers, butadiene-acrylonitrile-styrene copolymers, and mixtures thereof; (b) a polysaccharide; and (c) a polymer containing oxyalkylene monomers.
U.S. Pat. No. 5,208,093 (Carls et al.), the disclosure of which is totally incorporated herein by reference, discloses an electrographic article comprising a polymeric film having at least one polymeric receptor layer coated on at least one side thereof, said receptor layer having an equivalent or lower storage elasticity modulus than a toner resin used for forming images on the article.
Copending application U.S. Ser. No. 08/036,575, entitled "Transparent Recording Sheets," with the named inventor Shadi L. Malhotra, filed Mar. 19, 1993, the disclosure of which is totally incorporated herein by reference, discloses a substantially transparent recording sheet which comprises (a) a substantially transparent substrate; (b) a binder polymer coated on the substrate; and (c) particles of an antistatic component, said particles being present on at least the surface of the binder polymer coating.
While known materials and processes are suitable for their intended purposes, a need remains for improved recording sheets. In addition, there is a need for improved recording sheets suitable for use in ink jet printing processes. Further, a need remains for recording sheets which exhibit rapid drying times when imaged with aqueous inks. Additionally, a need remains for recording sheets coated with a discontinuous, porous film. A need also remains for recording sheets which are particularly suitable for use in printing processes wherein the recorded substrates are imaged with liquid inks and dried by exposure to microwave radiation. There is also a need for recording sheets which, subsequent to being imaged with an aqueous ink and dried by exposure to microwave radiation, exhibit little or no curling.